Let's roll up our sleeves and solve this. We have 648 and we're going to multiply it by 79, essentially adding 648 to itself 79 times.
Step 1: 0 + 648 = 648
Step 2: 648 + 648 = 1296
Step 3: 1296 + 648 = 1944
Step 4: 1944 + 648 = 2592
Step 5: 2592 + 648 = 3240
Step 6: 3240 + 648 = 3888
Step 7: 3888 + 648 = 4536
Step 8: 4536 + 648 = 5184
Step 9: 5184 + 648 = 5832
Step 10: 5832 + 648 = 6480
Step 11: 6480 + 648 = 7128
Step 12: 7128 + 648 = 7776
Step 13: 7776 + 648 = 8424
Step 14: 8424 + 648 = 9072
Step 15: 9072 + 648 = 9720
Step 16: 9720 + 648 = 10368
Step 17: 10368 + 648 = 11016
Step 18: 11016 + 648 = 11664
Step 19: 11664 + 648 = 12312
Step 20: 12312 + 648 = 12960
Step 21: 12960 + 648 = 13608
Step 22: 13608 + 648 = 14256
Step 23: 14256 + 648 = 14904
Step 24: 14904 + 648 = 15552
Step 25: 15552 + 648 = 16200
Step 26: 16200 + 648 = 16848
Step 27: 16848 + 648 = 17496
Step 28: 17496 + 648 = 18144
Step 29: 18144 + 648 = 18792
Step 30: 18792 + 648 = 19440
Step 31: 19440 + 648 = 20088
Step 32: 20088 + 648 = 20736
Step 33: 20736 + 648 = 21384
Step 34: 21384 + 648 = 22032
Step 35: 22032 + 648 = 22680
Step 36: 22680 + 648 = 23328
Step 37: 23328 + 648 = 23976
Step 38: 23976 + 648 = 24624
Step 39: 24624 + 648 = 25272
Step 40: 25272 + 648 = 25920
Step 41: 25920 + 648 = 26568
Step 42: 26568 + 648 = 27216
Step 43: 27216 + 648 = 27864
Step 44: 27864 + 648 = 28512
Step 45: 28512 + 648 = 29160
Step 46: 29160 + 648 = 29808
Step 47: 29808 + 648 = 30456
Step 48: 30456 + 648 = 31104
Step 49: 31104 + 648 = 31752
Step 50: 31752 + 648 = 32400
Step 51: 32400 + 648 = 33048
Step 52: 33048 + 648 = 33696
Step 53: 33696 + 648 = 34344
Step 54: 34344 + 648 = 34992
Step 55: 34992 + 648 = 35640
Step 56: 35640 + 648 = 36288
Step 57: 36288 + 648 = 36936
Step 58: 36936 + 648 = 37584
Step 59: 37584 + 648 = 38232
Step 60: 38232 + 648 = 38880
Step 61: 38880 + 648 = 39528
Step 62: 39528 + 648 = 40176
Step 63: 40176 + 648 = 40824
Step 64: 40824 + 648 = 41472
Step 65: 41472 + 648 = 42120
Step 66: 42120 + 648 = 42768
Step 67: 42768 + 648 = 43416
Step 68: 43416 + 648 = 44064
Step 69: 44064 + 648 = 44712
Step 70: 44712 + 648 = 45360
Step 71: 45360 + 648 = 46008
Step 72: 46008 + 648 = 46656
Step 73: 46656 + 648 = 47304
Step 74: 47304 + 648 = 47952
Step 75: 47952 + 648 = 48600
Step 76: 48600 + 648 = 49248
Step 77: 49248 + 648 = 49896
Step 78: 49896 + 648 = 50544
Step 79: 50544 + 648 = 51192

So, 648*79 = 51192